1
|
Sánchez Rivera FJ, Dow LE. How CRISPR Is Revolutionizing the Generation of New Models for Cancer Research. Cold Spring Harb Perspect Med 2024; 14:a041384. [PMID: 37487630 PMCID: PMC11065179 DOI: 10.1101/cshperspect.a041384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/26/2023]
Abstract
Cancers arise through acquisition of mutations in genes that regulate core biological processes like cell proliferation and cell death. Decades of cancer research have led to the identification of genes and mutations causally involved in disease development and evolution, yet defining their precise function across different cancer types and how they influence therapy responses has been challenging. Mouse models have helped define the in vivo function of cancer-associated alterations, and genome-editing approaches using CRISPR have dramatically accelerated the pace at which these models are developed and studied. Here, we highlight how CRISPR technologies have impacted the development and use of mouse models for cancer research and discuss the many ways in which these rapidly evolving platforms will continue to transform our understanding of this disease.
Collapse
Affiliation(s)
- Francisco J Sánchez Rivera
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Lukas E Dow
- Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, New York 10065, USA
- Department of Biochemistry, Weill Cornell Medicine, New York, New York 10065, USA
- Department of Medicine, Weill Cornell Medicine, New York, New York 10065, USA
| |
Collapse
|
2
|
Bruter AV, Varlamova EA, Okulova YD, Tatarskiy VV, Silaeva YY, Filatov MA. Genetically modified mice as a tool for the study of human diseases. Mol Biol Rep 2024; 51:135. [PMID: 38236499 DOI: 10.1007/s11033-023-09066-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 10/23/2023] [Indexed: 01/19/2024]
Abstract
Modeling a human disease is an essential part of biomedical research. The recent advances in the field of molecular genetics made it possible to obtain genetically modified animals for the study of various diseases. Not only monogenic disorders but also chromosomal and multifactorial disorders can be mimicked in lab animals due to genetic modification. Even human infectious diseases can be studied in genetically modified animals. An animal model of a disease enables the tracking of its pathogenesis and, more importantly, to test new therapies. In the first part of this paper, we review the most common DNA modification technologies and provide key ideas on specific technology choices according to the task at hand. In the second part, we focus on the application of genetically modified mice in studying human diseases.
Collapse
Affiliation(s)
- Alexandra V Bruter
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia, 119334
- Federal State Budgetary Institution "National Medical Research Center of Oncology Named After N.N. Blokhin" of the Ministry of Health of the Russian Federation, Research Institute of Carcinogenesis, Moscow, Russia, 115478
| | - Ekaterina A Varlamova
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia, 119334
- Federal State Budgetary Institution "National Medical Research Center of Oncology Named After N.N. Blokhin" of the Ministry of Health of the Russian Federation, Research Institute of Carcinogenesis, Moscow, Russia, 115478
| | - Yulia D Okulova
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia, 119334
| | - Victor V Tatarskiy
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia, 119334
| | - Yulia Y Silaeva
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia, 119334
| | - Maxim A Filatov
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia, 119334.
| |
Collapse
|
3
|
Yang C, Shitamukai A, Yang S, Kawaguchi A. Advanced Techniques Using In Vivo Electroporation to Study the Molecular Mechanisms of Cerebral Development Disorders. Int J Mol Sci 2023; 24:14128. [PMID: 37762431 PMCID: PMC10531473 DOI: 10.3390/ijms241814128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 09/12/2023] [Accepted: 09/13/2023] [Indexed: 09/29/2023] Open
Abstract
The mammalian cerebral cortex undergoes a strictly regulated developmental process. Detailed in situ visualizations, imaging of these dynamic processes, and in vivo functional gene studies significantly enhance our understanding of brain development and related disorders. This review introduces basic techniques and recent advancements in in vivo electroporation for investigating the molecular mechanisms underlying cerebral diseases. In utero electroporation (IUE) is extensively used to visualize and modify these processes, including the forced expression of pathological mutants in human diseases; thus, this method can be used to establish animal disease models. The advent of advanced techniques, such as genome editing, including de novo knockout, knock-in, epigenetic editing, and spatiotemporal gene regulation, has further expanded our list of investigative tools. These tools include the iON expression switch for the precise control of timing and copy numbers of exogenous genes and TEMPO for investigating the temporal effects of genes. We also introduce the iGONAD method, an improved genome editing via oviductal nucleic acid delivery approach, as a novel genome-editing technique that has accelerated brain development exploration. These advanced in vivo electroporation methods are expected to provide valuable insights into pathological conditions associated with human brain disorders.
Collapse
Affiliation(s)
- Chen Yang
- Human Anatomy and Histology and Embryology, School of Basic Medicine, Harbin Medical University, Harbin 150081, China
- Department of Human Morphology, Okayama University Graduate School of Medicine, Density and Pharmaceutical Sciences, Okayama 700-8558, Japan
| | - Atsunori Shitamukai
- Department of Human Morphology, Okayama University Graduate School of Medicine, Density and Pharmaceutical Sciences, Okayama 700-8558, Japan
| | - Shucai Yang
- Human Anatomy and Histology and Embryology, School of Basic Medicine, Harbin Medical University, Harbin 150081, China
| | - Ayano Kawaguchi
- Department of Human Morphology, Okayama University Graduate School of Medicine, Density and Pharmaceutical Sciences, Okayama 700-8558, Japan
| |
Collapse
|
4
|
Skavicus S, Heaton NS. Approaches for timeline reductions in pathogenesis studies using genetically modified mice. Microbiol Spectr 2023; 11:e0252123. [PMID: 37695101 PMCID: PMC10580824 DOI: 10.1128/spectrum.02521-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 07/22/2023] [Indexed: 09/12/2023] Open
Abstract
Although genetically modified mouse models have long been a powerful tool for microbiology research, the manipulation of the mouse genome is expensive, time consuming, and has historically remained the domain of dedicated animal facilities. The recent use of in vivo clustered regularly interspaced short palindromic repeats (CRISPR)-based editing technology has been reported to reduce the expertise, cost, and time required to generate novel mouse lines; it has remained unclear, however, if this new technology could meaningfully alter experimental timelines. Here, we report the optimization of an in oviduct murine genetic manipulation technique for use by microbiologists. We use this approach to generate a series of knockout mice and detail a protocol using an influenza A virus infection model to test the preliminary importance of a host factor in as short as 11 weeks (with a fully backcrossed knockout line in ~22 weeks) from initiation of the study. Broader use of this approach by the microbiology community will allow for more efficient, and rapid, definition of novel pathogenic mechanisms in vivo. IMPORTANCE Clustered regularly interspaced short palindromic repeats (CRISPR)-based technologies have already begun to revolutionize biomedical science. An emerging application of this technology is in the development of genetically modified model organisms to study the mechanisms underlying infectious disease. Here, we describe a protocol using an in vivo CRISPR-based approach that can be used to test the importance of a candidate host factor for microbial pathogenesis in less than 3 months and before complete establishment of a new mouse line. Adoption of this approach by the broader microbiology community will help to decrease the resources and time required to understand how pathogens cause disease which will ultimately speed up the development of new clinical interventions and therapies.
Collapse
Affiliation(s)
- Samantha Skavicus
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Nicholas S. Heaton
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina, USA
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, North Carolina, USA
| |
Collapse
|
5
|
Michalski MN, Williams BO. The Past, Present, and Future of Genetically Engineered Mouse Models for Skeletal Biology. Biomolecules 2023; 13:1311. [PMID: 37759711 PMCID: PMC10526739 DOI: 10.3390/biom13091311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 08/25/2023] [Accepted: 08/25/2023] [Indexed: 09/29/2023] Open
Abstract
The ability to create genetically engineered mouse models (GEMMs) has exponentially increased our understanding of many areas of biology. Musculoskeletal biology is no exception. In this review, we will first discuss the historical development of GEMMs and how these developments have influenced musculoskeletal disease research. This review will also update our 2008 review that appeared in BONEKey, a journal that is no longer readily available online. We will first review the historical development of GEMMs in general, followed by a particular emphasis on the ability to perform tissue-specific (conditional) knockouts focusing on musculoskeletal tissues. We will then discuss how the development of CRISPR/Cas-based technologies during the last decade has revolutionized the generation of GEMMs.
Collapse
Affiliation(s)
- Megan N. Michalski
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI 49503, USA;
| | - Bart O. Williams
- Department of Cell Biology, Van Andel Institute, Grand Rapids, MI 49503, USA;
- Core Technologies and Services, Van Andel Institute, Grand Rapids, MI 49503, USA
| |
Collapse
|
6
|
Aoto K, Takabayashi S, Mutoh H, Saitsu H. Generation of Flag/DYKDDDDK Epitope Tag Knock-In Mice Using i-GONAD Enables Detection of Endogenous CaMKIIα and β Proteins. Int J Mol Sci 2022; 23:11915. [PMID: 36233218 PMCID: PMC9569722 DOI: 10.3390/ijms231911915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 09/20/2022] [Accepted: 10/04/2022] [Indexed: 11/16/2022] Open
Abstract
Specific antibodies are necessary for cellular and tissue expression, biochemical, and functional analyses of protein complexes. However, generating a specific antibody is often time-consuming and effort-intensive. The epitope tagging of an endogenous protein at an appropriate position can overcome this problem. Here, we investigated epitope tag position using AlphaFold2 protein structure prediction and developed Flag/DYKDDDDK tag knock-in CaMKIIα and CaMKIIβ mice by combining CRISPR-Cas9 genome editing with electroporation (i-GONAD). With i-GONAD, it is possible to insert a small fragment of up to 200 bp into the genome of the target gene, enabling efficient and convenient tagging of a small epitope. Experiments with commercially available anti-Flag antibodies could readily detect endogenous CaMKIIα and β proteins by Western blotting, immunoprecipitation, and immunohistochemistry. Our data demonstrated that the generation of Flag/DYKDDDDK tag knock-in mice by i-GONAD is a useful and convenient choice, especially if specific antibodies are unavailable.
Collapse
Affiliation(s)
- Kazushi Aoto
- Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Shuji Takabayashi
- Laboratory Animal Facilities & Services, Preeminent Medical Photonics Education & Research Center, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Hiroki Mutoh
- Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Hirotomo Saitsu
- Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| |
Collapse
|
7
|
3R measures in facilities for the production of genetically modified rodents. Lab Anim (NY) 2022; 51:162-177. [PMID: 35641635 DOI: 10.1038/s41684-022-00978-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 04/22/2022] [Indexed: 12/30/2022]
Abstract
Sociocultural changes in the human-animal relationship have led to increasing demands for animal welfare in biomedical research. The 3R concept is the basis for bringing this demand into practice: Replace animal experiments with alternatives where possible, Reduce the number of animals used to a scientifically justified minimum and Refine the procedure to minimize animal harm. The generation of gene-modified sentient animals such as mice and rats involves many steps that include various forms of manipulation. So far, no coherent analysis of the application of the 3Rs to gene manipulation has been performed. Here we provide guidelines from the Committee on Genetics and Breeding of Laboratory Animals of the German Society for Laboratory Animal Science to implement the 3Rs in every step during the generation of genetically modified animals. We provide recommendations for applying the 3Rs as well as success/intervention parameters for each step of the process, from experiment planning to choice of technology, harm-benefit analysis, husbandry conditions, management of genetically modified lines and actual procedures. We also discuss future challenges for animal welfare in the context of developing technologies. Taken together, we expect that our comprehensive analysis and our recommendations for the appropriate implementation of the 3Rs to technologies for genetic modifications of rodents will benefit scientists from a wide range of disciplines and will help to improve the welfare of a large number of laboratory animals worldwide.
Collapse
|
8
|
Direct Injection of Recombinant AAV-Containing Solution into the Oviductal Lumen of Pregnant Mice Caused In Situ Infection of Both Preimplantation Embryos and Oviductal Epithelium. Int J Mol Sci 2022; 23:ijms23094897. [PMID: 35563284 PMCID: PMC9105285 DOI: 10.3390/ijms23094897] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 04/19/2022] [Accepted: 04/26/2022] [Indexed: 02/01/2023] Open
Abstract
Adeno-associated virus (AAV) vector is an efficient viral-based gene delivery tool used with many types of cells and tissues, including neuronal cells and muscles. AAV serotype 6 (AAV-6), one of numerous AAV serotypes, was recently found to efficiently transduce mouse preimplantation embryos. Furthermore, through coupling with a clustered, regularly interspaced, short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9) system—a modern genome editing technology—AAV-6 has been shown to effectively create a mutation at a target locus, which relies on isolation of zygotes, in vitro viral infection, and transplantation of the infected embryos to recipient females. Unfortunately, this procedure, termed “ex vivo handling of embryos”, requires considerable investment of capital, time, and effort. Direct transduction of preimplantation embryos through the introduction of AAV-6 into the oviductal lumen of pregnant females would be an ideal approach. In this study, we injected various types of recombinant AAV vectors (namely, rAAV-CAG-EGFP-1, -2, -5, and -6, each carrying an enhanced green fluorescent protein [EGFP] cDNA whose expression is under the influence of a cytomegalovirus enhancer + chicken β-actin promoter) into the ampulla region of oviducts in pregnant female mice at Day 0.7 of pregnancy (corresponding to the late 1-cell stage), and EGFP-derived green fluorescence was assessed in the respective morulae. The highest levels of fluorescence were observed in rAAV-CAG-EGFP-6. The oviductal epithelium was distinctly fluorescent. The fluorescence in embryos peaked at the morula stage. Our results indicate that intra-oviductal injection of AAV-6 vectors is the most effective method for transducing zona pellucida-enclosed preimplantation embryos in situ. AAV-6 vectors could be a useful tool in the genetic manipulation of early embryos, as well as oviductal epithelial cells.
Collapse
|
9
|
Hasegawa A, Mochida K, Nakamura A, Miyagasako R, Ohtsuka M, Hatakeyama M, Ogura A. Use of anti-inhibin monoclonal antibody for increasing the litter size of mouse strains and its application to i-GONAD. Biol Reprod 2022; 107:605-618. [PMID: 35368067 PMCID: PMC9382380 DOI: 10.1093/biolre/ioac068] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 03/08/2022] [Accepted: 03/25/2022] [Indexed: 11/20/2022] Open
Abstract
The litter size of mouse strains is determined by the number of oocytes naturally ovulated. Many attempts have been made to increase litter sizes by conventional superovulation regimens (e.g., using equine or human gonadotropins, eCG/hCG but had limited success because of unexpected decreases in the numbers of embryos surviving to term. Here, we examined whether rat-derived anti-inhibin monoclonal antibodies (AIMAs) could be used for this purpose. When C57BL/6 female mice were treated with an AIMA and mated, the number of healthy offspring per mouse increased by 1.4-fold (11.9 vs. 8.6 in controls). By contrast, treatment with eCG/hCG or anti-inhibin serum resulted in fewer offspring than in nontreated controls. The overall efficiency of production based on all females treated (including nonpregnant ones) was improved 2.4 times with AIMA compared with nontreated controls. The AIMA treatment was also effective in ICR mice, increasing the litter size from 15.3 to 21.2 pups. We then applied this technique to an in vivo genome-editing method (improved genome-editing via oviductal nucleic acid delivery, i-GONAD) to produce C57BL/6 mice deficient for tyrosinase. The mean litter size following i-GONAD increased from 4.8 to 7.3 after the AIMA treatment and genetic modifications were confirmed in 80/88 (91%) of the offspring. Thus, AIMA treatment is a promising method for increasing the litter size of mice and may be applied for the easy proliferation of mouse colonies as well as in vivo genetic manipulation, especially when the mouse strains are sensitive to handling.
Collapse
Affiliation(s)
- Ayumi Hasegawa
- RIKEN BioResource Research Center, Tsukuba, Ibaraki, Japan
| | - Keiji Mochida
- RIKEN BioResource Research Center, Tsukuba, Ibaraki, Japan
| | - Ayaka Nakamura
- Support Center for Medical Research and Education, Tokai University, Kanagawa, Japan
| | - Rico Miyagasako
- Division of Basic Medical Science and Molecular Medicine, School of Medicine, Tokai University, Kanagawa Japan
| | - Masato Ohtsuka
- Division of Basic Medical Science and Molecular Medicine, School of Medicine, Tokai University, Kanagawa Japan
- The Institute of Medical Sciences, Tokai University, Kanagawa, Japan
| | | | - Atsuo Ogura
- RIKEN BioResource Research Center, Tsukuba, Ibaraki, Japan
- Graduate School of Life and Environmental Science, University of Tsukuba, Tsukuba, Ibaraki, Japan
- Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan
- RIKEN Cluster for Pioneering Research, Wako, Saitama, Japan
| |
Collapse
|
10
|
Generation of mouse conditional knockout alleles in one step using the i-GONAD method. Genome Res 2020; 31:121-130. [PMID: 33328166 PMCID: PMC7849380 DOI: 10.1101/gr.265439.120] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 11/16/2020] [Indexed: 12/12/2022]
Abstract
The Cre/loxP system is a powerful tool for gene function study in vivo. Regulated expression of Cre recombinase mediates precise deletion of genetic elements in a spatially– and temporally–controlled manner. Despite the robustness of this system, it requires a great amount of effort to create a conditional knockout model for each individual gene of interest where two loxP sites must be simultaneously inserted in cis. The current undertaking involves labor-intensive embryonic stem (ES) cell–based gene targeting and tedious micromanipulations of mouse embryos. The complexity of this workflow poses formidable technical challenges, thus limiting wider applications of conditional genetics. Here, we report an alternative approach to generate mouse loxP alleles by integrating a unique design of CRISPR donor with the new oviduct electroporation technique i-GONAD. Showing the potential and simplicity of this method, we created floxed alleles for five genes in one attempt with relatively low costs and a minimal equipment setup. In addition to the conditional alleles, constitutive knockout alleles were also obtained as byproducts of these experiments. Therefore, the wider applications of i-GONAD may promote gene function studies using novel murine models.
Collapse
|
11
|
Abstract
The mouse is one of the most widely used model organisms for genetic study. The tools available to alter the mouse genome have developed over the preceding decades from forward screens to gene targeting in stem cells to the recent influx of CRISPR approaches. In this review, we first consider the history of mice in genetic study, the development of classic approaches to genome modification, and how such approaches have been used and improved in recent years. We then turn to the recent surge of nuclease-mediated techniques and how they are changing the field of mouse genetics. Finally, we survey common classes of alleles used in mice and discuss how they might be engineered using different methods.
Collapse
Affiliation(s)
- James F Clark
- Department of Cell, Developmental, and Regenerative Biology, Icahn School of Medicine at Mt. Sinai, New York, New York 10029, USA
| | - Colin J Dinsmore
- Department of Cell, Developmental, and Regenerative Biology, Icahn School of Medicine at Mt. Sinai, New York, New York 10029, USA
| | - Philippe Soriano
- Department of Cell, Developmental, and Regenerative Biology, Icahn School of Medicine at Mt. Sinai, New York, New York 10029, USA
| |
Collapse
|
12
|
Horii T, Kobayashi R, Kimura M, Morita S, Hatada I. Calcium-Free and Cytochalasin B Treatment Inhibits Blastomere Fusion in 2-Cell Stage Embryos for the Generation of Floxed Mice via Sequential Electroporation. Cells 2020; 9:cells9051088. [PMID: 32354036 PMCID: PMC7290713 DOI: 10.3390/cells9051088] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 04/24/2020] [Accepted: 04/27/2020] [Indexed: 01/10/2023] Open
Abstract
The generation of conditional knockout mice using the Cre-loxP system is advantageous for the functional analysis of genes. Flanked by two loxP sites (floxed) mice can be directly obtained from fertilized eggs by the CRISPR/Cas9 genome editing system. We previously reported that sequential knock-in (KI) of each loxP site by electroporation (EP) at the 1- and 2-cell embryonic stages increases the number of mice with floxed alleles compared with simultaneous KI. However, EP at the 2-cell stage frequently induced blastomere fusion. These fused embryos cannot develop to term because they are tetraploidized. In this study, we examined the following three conditions to inhibit blastomere fusion by EP at the 2-cell stage: (1) hypertonic treatment, (2) Calcium (Ca2+)-free treatment, and (3) actin polymerization inhibition. Hypertonic treatment of 2-cell stage embryos prevented blastomere fusion and facilitated blastocyst development; however, KI efficiency was decreased. Ca2+-free treatment and actin polymerization inhibition by cytochalasin B (CB) reduced fusion rate, and did not have negative effects on development and KI efficiency. These results suggest that Ca2+-free and CB treatment at the 2-cell stage is effective to generate floxed mice in combination with a sequential EP method.
Collapse
|